The present invention relates to saws, particularly to saws for cutting wafers for optical and electronic applications, for example, and more particularly to a hydrodynamic blade guide or bearing for a saw which retains the saw blade centered in the saw kerf.
Cutting or slicing of materials, such as utilized in optical and electronic applications, as well as ceramics, glass, and brittle composite material is an expensive process and generally results in damaged, non-smooth, and non-flat surfaces. Substantial effort has been directed to resolve the problems associated with cutting of such materials.
Materials from which wafers are cut include optical and electronic materials in boule form such as KDP, GaAs, and silicon, as well as other brittle materials. The initial operation in manufacturing wafers from boules is the slicing or cutting process. Slicing currently suffers from its inability to produce flat surfaces free from sub-surface damage while maintaining long saw blade life and small saw kerf. The significant penalty associated with this slicing process derives not just from the cost of the sawing operation but also from the cost of subsequent processes to remove damage and to planarize the surface which are made necessary by the sawing or slicing operation. In addition, not only do the above-described slicing or cutting problems come into play, but also the cost of wasted materials lost to the saw kerf must be considered. The smaller the kerf, the greater the number of usable wafers cut from a boule.
Thus, there has been a need for a means or method by which slicing of boules, for example, can be effectively and efficiently carried out. This need is satisfied by the present invention, which utilizes a self-pumped hydrodynamic blade guide or bearing which functions to maintain the saw blade centered in the saw kerf in the workpiece. The blade guide or bearing utilizes relieved pockets or grooves on the sides of the saw blade which entrain cutting fluid, and the saw kerf in the workpiece itself provides the stator surface, whereby the trapped fluid provides pressure between the blade and the workpiece as an inverse function of the gaps between the blade surface and the workpiece surface, which results in maintaining the saw blade centered in the saw kerf.
An object of the present invention is to provide for improved cutting of materials that are difficult to cut.
A further object of the invention is to provide a guide or bearing for a saw blade.
A further object of the invention is to provide a means and method of maintaining a saw blade centered in a saw kerf.
Another object of the invention is to provide a self-pumped hydrodynamic bearing or guide for a saw.
Another object of the invention is to enable cutting or slicing of boules of material, such as silicon, KDP, GaAs, and other composite materials, which produce surfaces that are flat and free from sub-surface damage.
Another object of the invention is to provide a saw blade with relieved pockets or grooves which entrain cutting fluid which provides pressure between the blade side surfaces and the workpiece thereby causing the blade to be maintained in the center of the saw kerf.
Other objects and advantages of the invention will become apparent from the following description and accompanying drawings. The invention broadly involves a means and method for maintaining a saw blade centered in a saw kerf. More specifically the invention involves a precision saw capable of cutting material such that the cuts are flat and there is no sub-surface damage, while maintaining long saw blade life and a small saw kerf. Thus, utilizing the means and method of the present invention cuts can be make such that conventional subsequent processes to remove damage and to planarize the surface are eliminated.
The specific advantages of the saw of the present invention are: 1) long blade life, 2) small kerf, 3) reduced subsurface damage, and 4) good control of the surface flatness. This is accomplished by a precision saw which uses a self-pumped hydrodynamic guide or bearing where features, such as relieved pockets or grooves, are incorporated into the sides of the saw blade, with the saw kerf in the workpiece itself providing the bearing guide or stator surface. The features formed in both sides of the saw blade entrain cutting fluid as the blade enters the kerf in the workpiece. The trapped fluid provides pressure between the sides of the blade and the workpiece as an inverse function of the gaps between the saw blade surfaces and the workpiece surfaces. If the blade de-centers in the kerf, then one gap will increase and one gap will decrease and the consequent pressure difference between the two sides of the blade will cause the blade to re-center itself in the kerf.